Serotonin has been implicated in a number of diseases, disorders, and conditions that originate in the central nervous system, including diseases, disorders, and conditions related to, for example, sleeping, eating, perceiving pain, controlling body temperature, controlling blood pressure, depression, anxiety, addiction and schizophrenia. Serotonin also plays an important role in peripheral systems, such as the gastrointestinal system, where it has been found to mediate a variety of contractile, secretory and electrophysiologic effects.
Because of the broad distribution of serotonin within the body, there is a need for drugs that affect serotonergic systems. In particular, agonists, partial agonists, and antagonists of serotonergic systems are of interest for the treatment of a wide range of disorders, including anxiety, depression, hypertension, migraine, obesity, compulsive disorders, schizophrenia, autism, neurodegenerative disorders (e.g., Alzheimer's disease, Parkinsonism and Huntington's chorea), and chemotherapy-induced vomiting.
The major classes of serotonin receptors (5-HT1-7) contain one to seven separate receptors that have been formally classified. See Glennon, et al., Neuroscience and Behavioral Reviews, 1990, 14, 35; and D. Hoyer, et al. Pharmacol. Rev. 1994, 46, 157-203.
For example, the 5-HT2 family of receptors contains 5-HT2a, 5-HT2b, and 5-HT2c subtypes, which have been grouped together on the basis of primary structure, secondary messenger system, and operational profile. All three 5-HT2 subtypes are G-protein coupled, activate phospholipase C as a principal transduction mechanism, and contain a seven-transmembrane domain structure. There are distinct differences in the distribution of the three 5-HT2 subtypes in a mammal. The 5-HT2b and 5-HT2a receptors are widely distributed in the peripheral nervous system, with 5-HT2a also found in the brain. The 5-HT2c receptor has been found only in the central nervous system, being highly expressed in many regions of the human brain. See G. Baxter, et al. Trends in Pharmacol. Sci. 1995, 16, 105-110.
Subtype 5-HT2a has been associated with effects including vasoconstriction, platelet aggregation, and bronchoconstriction, as well as certain CNS effects, while subtype 5-HT2c has been associated with diseases that include depression, anxiety, obsessive compulsive disorder, addiction, panic disorders, phobias, psychiatric syndromes, and obesity. Very little is known about the pharmocologic role of the 5-HT2b receptor. See F. Jenck, et al., Exp. Opin. Invest. Drugs, 1998, 7, 1587-1599; M. Bos, et al., J. Med. Chem., 1997, 40, 2762-2769; J. R. Martin, et al., The Journal of Pharmacology and Experimental Therapeutics, 1998, 286, 913-924; S. M. Bromidge, et al., 1. Med. Chem., 1998, 41, 1598-1612; G. A. Kennett, Drugs, 1998, 1, 4, 456-470; and A. Dekeyne, et al., Neuropharmacology, 1999, 38, 415-423.
WO 93/13105, U.S. Pat. Nos. 5,691,330 and 5,532,240 disclose thiophene derivatives; U.S. Pat. No. 4,414,225 discloses thiophene, furan and pyrrole derivatives; U.S. Pat. No. 4,575,504 discloses thienothiazole derivatives; U.S. Pat. No. 5,258,378 discloses certain pyrroloazepine compounds; U.S. Pat. Nos. 4,414,225 and 4,904,653 disclose certain azepine derivatives; WO 2005/019179 discloses certain benzazepines, WO 2005/003096, WO 2005/042490, and WO 2005/042491 disclose benzazepine derivatives; WO 96/11201 discloses furan derivatives; WO 2005/040169 discloses certain fused pyrrole- and pyrazole-containing heterocyclic compounds which are serotonin modulators; WO 2004/024065 discloses substituted bicyclic thiophene derivatives. None of these patents or patent applications disclose compounds of the instant invention.